1. Field of the Invention
The present invention relates to a surface-treating apparatus and a surface-treating method and, more particularly, to a surface-treating apparatus and a surface-treating method for improving discharging of various gases deposited on the surface of an object to be treated, e.g., a semiconductor wafer.
2. Description of the Related Art
A surface-treating apparatus, e.g., an etching apparatus, is used in a step of forming a fine circuit pattern of a semiconductor device.
As a conventional etching apparatus, an etching apparatus having the following structure is known. A process chamber (etching process chamber) includes a gas exhaust pipe and an etching gas supply pipe. An upper electrode and a lower electrode are arranged in the etching process chamber to be opposite to each other. An RF power supply is connected to, e.g., the lower electrode. A load lock chamber having a convey mechanism is connected to the etching process chamber. A gas exhaust pipe and an inert gas supply pipe are connected to the load lock chamber. A gate valve is inserted to the connection portion between the etching process chamber and the load lock chamber. The load lock chamber is used to load an object to be treated, e.g., a semiconductor wafer, in the etching process chamber set in a low-pressure atmosphere or unload the etched wafer unloaded from the etching process chamber after the wafer is set in an atmospheric pressure.
In order to etch a semiconductor wafer using the above etching apparatus, after the semiconductor wafer is loaded in the load lock chamber, gases in the load lock chamber and the etching process chamber are exhausted through the gas exhaust pipes, respectively, to obtain a desired low-pressure atmosphere. Subsequently, the gate valve is opened, and the semiconductor wafer in the load lock chamber is conveyed on the lower electrode in the etching process chamber by the convey mechanism. The gate valve is closed, and while the gas is continuously exhausted, an etching gas is supplied from the etching gas supply pipe to the etching process chamber. When the low-pressure state of the etching process chamber is stabled, an RF power is supplied from the RF power supply to the lower electrode. At this time, a plasma is generated between the upper electrode and the lower electrode, and the etching gas supplied to the etching process chamber is activated. The activated etching gas and ions act on the semiconductor wafer placed on the lower electrode to perform etching.
A more fine circuit pattern has been demanded according to an increase in integration density of a semiconductor device. In response to this demand, the following technique is developed. When a semiconductor wafer is etched using the above etching apparatus, the etching is performed while the semiconductor wafer is cooled at minus several tens of .degree. C.
However, the above conventional technique has the following problems.
That is, since the semiconductor wafer is arranged in the etching process chamber set in a low-pressure atmosphere and is etched while it is cooled, an etching gas (e.g., chlorine-based gas) is deposited on the surface of the semiconductor wafer. After the etched semiconductor wafer is conveyed in the load lock chamber and set in an atmospheric pressure, it is unloaded in the air. Since the semiconductor wafer conveyed in the load lock chamber has a low temperature, e.g., about 0.degree. C, the semiconductor wafer on which the chlorine-based gas is deposited is unloaded from the load lock chamber in the air. As a result, the semiconductor wafer unloaded in the air discharges harmful chlorine-based gas from its surface in a process of increasing the temperature of the semiconductor wafer to room temperature. The chlorine-based gas discharged in the air corrodes peripheral equipments of the etching apparatus not only to generate particles serving as secondary pollution sources but to adversely affect operators.
In addition, the chlorine-based gas deposited on the surface of the semiconductor wafer reacts with the wafer to generate reaction products, thereby considerably degrading the appearance of the semiconductor wafer.
When the cooled semiconductor wafer is unloaded in the air, droplets are attached to the surface of the semiconductor wafer. Since the droplets react with chlorine-based gas adsorbed in the wafer to generate a hydrochloric acid solution, the semiconductor wafer is wet-etched by the hydrochloric acid solution. As a result, etching accuracy is considerably degraded.